Activity sheet – Solids, liquids and gases
What is diffusion?
Diffusion occurs when particles move from where there are lots of particles (high
concentration) to where there are fewer particles (low concentration). Solids cannot diffuse
because their particles are too close together and are strongly attracted to each other.
Liquids and gases are able to diffuse. Gases diffuse the quickest because their particles are
free to move quickly in different directions. When a liquid or gas is heated, it diffuses more
quickly.
1 Read the following passage and circle the correct word in each pair.
The (movement/shrinking) of particles is called diffusion. A substance spreads out from an
area where there is (more/less) of the substance to an area where there is (more/less).
Gases diffuse (quickly/slowly) because the particles are moving quickly in all directions.
Liquids can also diffuse but the particles move more (slowly/quickly).
Solid particles cannot diffuse because they cannot move, they can only (vibrate/slide over
each other). An odour is a (gas/liquid) that is given off by a substance. You can smell
perfume because the scent particles diffuse through the air to your nose in the form of a
(solid/gas). If you drop a little bit of dye into a jar of water the colour will spread slowly
through the water. This is an example of diffusion in (liquids/gases). When particles are
(heated/cooled), they diffuse more quickly.
2 List three examples of diffusion. (HINT: Look at the picture on this page.)
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3 Choose the correct ending for each of the following sentences.
Sentence start
Sentence endings
Diffusion means ....
contracting.
spreading out.
expanding.
A substance diffuses
from an area of high
concentration to an
area of ......
the same
concentration.
high
concentration.
low
concentration.
Gases diffuse .........
quickly.
slowly.
only at very high
temperatures.
A dye will diffuse more
quickly in .........
cold water.
room-temperature
water.
hot water.
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ACHIEVE! Science understanding – Chemistry for years 7–8
© Janine Haeusler and Blake Education 2014